By Agence France-Presse
Some addicts are forced by law to spend up to two years in Vietnam's rehab centers, while others are admitted by family or check themselves in.
Most detainees undergo cold-turkey treatment in the notoriously overcrowded centres or are subjected to solitary confinement for breaking rules.
Several breakouts have occurred in recent years and the most recent started on Saturday morning in the southern province of Tien Giang, a police officer told AFP on condition of anonymity, adding that about half the escapees had already been captured.
"There are around 100 addicts still on the run and the police are still looking for them," the officer said.
A disagreement with staff escalated into an assault, with patients wielding knives and bricks and encouraging others to break down the door, state-controlled website VnExpress reported.
Images circulating on social media showed dozens of men, many shirtless, wandering on a highway near the rehab centre.
"They passed my area holding canes and shouted like protesters. When we saw them, me and people around were scared and worried," local resident Le Hai Trieu told AFP.
Residents pitched in to help local authorities capture the men.
Another state media outlet said that more than 650 people are registered at the Tien Giang facility, but it did not provide figures on the number of voluntary admissions.
There are more than 220,000 registered drug addicts in Vietnam, according to official statistics released last year, with heroin and methamphetamine the most popular narcotics.
While Vietnam is experimenting with more community-based treatment options in response to criticism over the centres, they remain the most-used form of recovery.
The centres are widely supported as a viable treatment option although addiction specialists say they don't work and relapse rates are high.
Early last year 100 people escaped from a centre in southern Long An province because they were upset about spending the annual Tet new year holiday away from their homes.